Combination of bolt and nut is widely used as a fundamental fastening elements. The bolt has a head portion formed as a larger outer diameter portion at one end of the shaft, and an outer thread formed on the circumference of the shaft for engaging with inner thread of the nut. The objects are fastened between the head portion and the nut, and the fastening force between them is adjusted by tightening the nut, and the fastening length is adjusted by using washer or spacer.
In a smelting reduction plant and the like, it is preferable to make a bottom portion of a reduction furnace separable, because interior of the bottom portion is covered with a firebrick lining which needs periodical repair. This separable construction of the furnace makes the plant more cost effective than to install two furnaces so that one furnace can be repaired while the other furnace is in operation. The smelting furnace in the commercial plant has a large volume, and a large number of fastening bolts are needed for connecting the bottom portion to the furnace body with flanges. Air tightness is required at the flange connecting portion because the smelting reduction furnace is operated under high internal pressure of several kgf/cm2 G, and quick replacement of the bottom portion is also required to prevent drop of plant operating efficiency. When conventional bolts and nuts are used for fastening flanges, a large number of bolts and nuts should be fastened uniformly to keep air tightness, and unfastened for releasing flanges.
FIG. 11 shows a prior art of a bolt disclosed in Japanese Utility Model Laid-Open No. Sho 63-157407, which is fastened utilizing hydraulic pressure. A guide base 1a is secured on a rest bar 3 by fastening a clamp 2, and by unfastening the clamp 2 the rest bar 3 is slidable along the rest bar 3 in the direction perpendicular to the surface of the drawing. A fastening shaft 4 for creating fastening force is inserted into a piston 5 combined with a cylinder 8. When the hydraulic pressure is applied to create a hydraulic space 6 at the abutted portion of piston 5 and cylinder 8, a lock nut 7 attached on the end of the shaft 4 is pushed apart by the piston 5 in the axial direction of the shaft 4. A reaction force of the piston 5 against the lock nut 7 is applied on the clamp 2 by the cylinder 8.
Upper half of FIG. 11 shows the condition when no hydraulic pressure is applied. In this condition, the end surface of the cylinder 8 is fastened by a fastening nut 9 attached on the circumference of the piston 5. When the hydraulic pressure is applied to create hydraulic pressurizing space 6 between the abutted portions of the piston 5 and the cylinder 8, as shown in lower half of the FIG. 11, the piston 5 is moved in the direction away from the head portion of the fastening shaft 4, and a gap G is formed between end surfaces of the cylinder 8 and the fastening nut 9. Under such condition, the lock nut 7 is pushed by the piston 5 away from the head portion 4 to extend the shaft 4 in axial direction. When the gap G is formed, the fastening nut 9 is rotated to come into contact again with the end surface of the cylinder 8. Relative movement between the piston 5 and the cylinder 8 is then restricted by the fastening nut 9, and the position of the lock nut 7 shown in the lower half of the FIG. 11 can be maintained after the hydraulic pressure is released. A convex nut 12 and a concave nut 13 are disposed between the clamp 2 and the cylinder 8, and a spacer 14 is disposed between the end surfaces of the piston 5 and the lock nut 7.
By using a bolt shown in FIG. 11, a large number of bolts can be securely fastened utilizing hydraulic pressure. Another prior arts of such bolts utilizing hydraulic pressure for fastening are disclosed in Japanese Laid-Open Patent Publication No. Hei 2-262971 and Japanese Laid-Open Patent Publication No. Hei 5-79302. The former includes means for creating fastening force in a turn buckle by extending the bolt with hydraulic pressure, and means for locking the fastened condition after the hydraulic pressure is released. The latter includes tension nuts connected at both ends of the bolt, and one tension nut is pulled up by a hydraulic cylinder to create prescribed fastening force, and the pulled up condition is retained by fastening a nut.
By applying bolt designs disclosed in Japanese Laid-Open Utility Model No. Sho 63-157407, Japanese Laid-Open Patent No. Hei 2-262971 or Japanese Laid-Open Patent Publication No. Hei 5-79302 for fastening objects such as flanges, a large number of bolts can be fastened simultaneously utilizing hydraulic pressure, but it is difficult to unfasten the objects by loosening the bolts. In the prior art of Japanese Laid-Open Utility Model No. Sho 63-157407 shown in FIG. 11, the gap G is formed again between the fastening nut 9 and the cylinder 8 by the application of additional hydraulic pressure in the hydraulic space 6, and the fastening nut 9 can be loosened by hand. However, the lock nut 7 is pushed strongly against the end of the piston 5, and a considerable amount of torque will be needed to loosen the lock nut 7 from the fastening shaft 4. The clamp 2 cannot be removed from the guide base 1a and the rest bar 3 without removing the lock nut 7 from the fastening shaft 4. When the fastening shaft 4 together with the combination of piston 5 and cylinder 8 as shown in FIG. 11 is applied for fastening flanges, the flanges cannot be separated without removing the lock nut 7 from the fastening shaft 4.
Fastening and unfastening operation of the bolt can be automatically done by rotating the nut with a hydraulic motor or other means. However, this method has following disadvantages:
(1) The equipment becomes expensive;
(2) Complicated and expensive hydraulic apparatus is needed;
(3) Large installation space is needed when the hydraulic apparatus is relatively large, and the installation becomes difficult due to the interference of the apparatus when the flange has a large diameter and needs a large number of bolt for fastening.
Manual fastening and unfastening operation of ordinary bolt and nut has following disadvantages:
(1) Manual operation becomes difficult when the bolt has a large diameter;
(2) Insertion and withdrawal of the bolt is difficult due to its heavy weight;
(3) Even when the clamp is manually operable, long time is needed to perform the entire operation of fastening or unfastening a large number of bolts, lowering plant operation efficiency;
(4) Fastening force of the bolt is required to be adjusted precisely for respective fastening operation by a torque wrench or other means.
The object of the present invention is to provide a fastening bolt with a simple structure with easy fastening and unfastening operation, and with no adjustment of the fastening force is required in respective fastening operation.
The fastening bolt of the present invention is for fastening an object between a head portion formed on one end of the shaft and a nut attached on the threaded portion formed around the shaft, characterized in that the fastening bolt includes a hydraulic pressure application means for applying a hydraulic pressure to extend the shaft between the head portion and the threaded portion of the bolt when the object is fastened between the head portion and the nut, and for releasing the fastened condition of the object, and the head portion is formed in a hammer shape by a removably attached cotter which extends in the direction perpendicular to the axis of the shaft.
According to the present invention of the above structure, the shaft of the fastening bolt can be extended between the head portion and the nut where the object is fastened by the application of hydraulic pressure, and when the shaft is extended, the nut can easily be loosened for releasing the fastened condition. By tightening the nut when the shaft is extended, large fastening force is obtained after the hydraulic pressure is released, and the fastening force can also be adjusted easily by the adjustment of the hydraulic pressure. More particularly, the object is fastened between the head portion and the nut attached on the threaded portion, and the shaft is extended between the head portion and the nut by the application of hydraulic pressure by the hydraulic pressure application means, and fastened condition of the object is released to become unfastened condition. In the unfastened condition, the nut can be easily rotated and can also be removed from the shaft. By tightening the nut when the shaft is extended, the object can be tightly fastened between the nut and the head portion after the hydraulic pressure is released. This fastening condition corresponds to the condition when the nut is tightened with relatively strong fastening force. The force needed to tighten the nut while the shaft is extended by the hydraulic pressure can be set to such an extent that the nut is manually rotatable, and the final fastening force can be adjusted by the hydraulic pressure.
The present invention is further characterized in that a cavity is formed within the shaft to be extended, and the fluid pressurizing means is adapted to apply and release hydraulic pressure in the cavity.
According to the invention of the above structure, the shaft can be extended by a simple construction because the shaft is extended by the application of hydraulic pressure in the cavity. More particularly, when the cavity formed within the shaft is pressurized by the fluid pressurizing means, the shaft is extended by the internal pressure in the cavity, and the shaft returns to its original length when the hydraulic pressure in the cavity is released.
Further, the head portion is formed in a hammer shape by a removably attached cotter which extends in the direction perpendicular to the axis of the shaft. Therefore, the fastening bolt can easily be withdrawn from the object by removing the cotter from the head portion. More particularly, when the cotter extending in the direction perpendicular to the axis of the shaft is attached, the head portion is prevented from passing through the bolt hole with a slightly larger inner diameter than the outside diameter of the shaft of the fastening bolt, enabling the object to be fastened. When the cotter is removed from the head portion of the fastening bolt, the shaft of the fastening bolt can easily be withdrawn through the bolt hole formed in the object, and can be easily withdrawn from the bolt hole to release the object.
The present invention is further characterized in that the means for applying pressure includes a combination of cylinder and piston, wherein the cylinder and the piston are moved apart in the axial direction of the shaft by the application of hydraulic pressure, and wherein either one of the cylinder or the piston is connected to the shaft, and the other one of the cylinder or the piston pushes the nut away from the head portion by application of the hydraulic pressure.
According to the present invention of the above structure, the combination of cylinder and piston is provided for the extension of the shaft, which is profitable for a small diameter shaft in which it is difficult to form a cavity. More particularly, the combination of cylinder and piston is provided in the fluid pressurizing means. When the hydraulic pressure is applied, the cylinder and piston are moved apart each other in the axial direction of the shaft of the fastening bolt, and either one of the cylinder or piston is connected to the shaft and the other one of the cylinder or the piston presses the nut away from the head portion, thus, the shaft can be extended by the application of hydraulic pressure to separate apart between the shaft and the nut.
Further, a bolt hole which corresponds to the shape of the fastening bolt is formed in the object, and the fastening bolt can be easily withdrawn from the object. More particularly, the head portion of the fastening bolt is formed in a hammer shape which extends in the direction perpendicular to the axis of the shaft, and the bolt hole in the object is formed as an elongated shape which corresponds to the hammer shape. The head portion and the bolt hole cross each other in the fastened condition, and the head portion is alined with the bolt hole in the unfastened condition, thus the fastening and unfastening condition can be converted easily by rotating the head portion.
The present invention is further characterized in that a collar extending in the axial direction of the shaft is provided between the fastened object and the nut.
According to the present invention of the above structure, the shaft can be extended sufficiently by a relatively low pressure because the length of the shaft is increased by the collar. More particularly, the collar extending in the axial direction of the shaft is provided between the fastened object and the nut, increasing the length of the extendable portion of the shaft, within which the fluid pressurizing means is easily mounted.
The present invention is further characterized in that the object is fastened via spherical washers.
According to the present invention of the above structure, uniform fastening force is obtained by the spherical washers. More particularly, the object is fastened via spherical washers having centering function to apply uniform fastening force around the axis of the shaft.
The present invention is further characterized in that the head portion is formed in a hammer shape having an axis extending in the direction perpendicular to the axial direction of the shaft.
According to the present invention of the above structure, a bolt hole which corresponds to the particular shape of the head portion is formed in the object, and the fastening bolt can be easily withdrawn from the object. More particularly, the head portion of the fastening bolt is formed in hammer shape which extends in the direction perpendicular to the axial direction of the shaft, and the bolt hole in the object is formed as an elongated shape which corresponds the hammer shape. The head portion and the bolt hole cross each other in the fastened condition, and the head portion is alined with the bolt hole in the unfastened condition, thus, the fastening and unfastening condition can be converted easily by rotating the head portion.
The present invention is further characterized in that the head portion is formed by a removably attached cotter which extends in the direction perpendicular to the axial direction of the shaft.
According to the present invention of the above structure, the fastening bolt can be easily withdrawn from the object by removing the cotter form the head portion. More particularly, when the cotter is attached, the head portion of the fastening bolt is prevented from passing through the bolt hole with a slightly larger inner diameter than the shaft of the fastening bolt, enabling the object to be fastened. When the cotter is removed from the head portion of the fastening bolt, the shaft of the fastening bolt can pass the bolt hole formed in the object, and can be easily withdrawn from the bolt hole to release the object.
The present invention is further characterized in that the nut is fastened via a spacer having a non circular irregular sectional shape in a plane perpendicular to the axial direction of the shaft.
According to the present invention of the above structure, the object to be fastened has a bolt hole through which non circular spacer can pass, and the fastening bolt can be easily withdrawn from the object by aligning the direction of the non circular spacer with the bolt hole. More particularly, the nut for fastening the object with the fastening bolt is fastened via spacer having a non circular irregular sectional shape in a plane perpendicular to the axial direction of the shaft, the fastening the object and removal of the bolt from the object can be performed easily by the bolt hole having a shape that the fastening bolt together with the nut can pass when the non circular shaped spacer is oriented in the predetermined direction, and cannot pass when the spacer is oriented in another direction.
The present invention is further characterized in that the hammer shaped head portion is not formed integrally with the shaft, but is formed separately as a spacer, and another nut is disposed outside of the head portion opposite from the object for limiting the movement of the hammer shaped head portion in the axial direction of the shaft.
According to this invention of the above structure, a hole is provided in the center of the hammer shaped head portion to make the head portion freely rotatable around the shaft and enabling it to serve as a spacer, and by providing another nut threadably connected to the shaft on the outer side of the head portion, the position for limiting the movement of the hammer shaped head in the axial direction of the shaft can be easily adjusted when the fastening bolt is in the unfastened condition.